1. 
[syn: necessarily, needfully]
The Collaborative International Dictionary of English v.0.48:
Needful \Need"ful\ (n[=e]d"f[.u]l), a.
   1. Full of need; in need or want; needy; distressing.
      [Archaic] --Chaucer.
      [1913 Webster]
            The needful time of trouble.          --Bk. of Com.
                                                  Prayer.
      [1913 Webster]
   2. Necessary for supply or relief; requisite.
      [1913 Webster]
            All things needful for defense abound. --Dryden.
      [1913 Webster] -- Need"ful*ly, adv. -- Need"ful*ness,
      n.
      [1913 Webster]
WordNet (r) 3.0 (2006):
needfully
    adv 1: in an essential manner; "such expenses are necessarily
           incurred" [syn: necessarily, needfully] [ant:
           unnecessarily]